People have pressured me to watch this anime, and I finally did, gave it a go from the top to bottom, and although, the theme of the anime is about high schoolers transferring into another world to find fulfilment and salvation, the whole thing about the NPCs didn't really go along, like why were they there in the first place? Why no one of them realized that they had been taking the classes perpetually without getting anywhere?
How the softwares worked and how were they was Angel able to create weapons all of her own? Why there was a manual for it? Why didn't they destroy it and took it for themselves. I know the anime is very old, but they are many loopholes in the anime. Think I heard that the creator of this anime also made Charlotte, which was a lot better than this, but with a similar highschool theme in mind. And if you think about it, the characters in that anime do resemble the characters in Angel Beats.
Decent anime with unexplainable loopholes, but hey this is just another anime!